Eruptive activity at Kasatochi volcano has declined gradually over the past week. Seismic activity is still being detected by the AVO seismic network on Great Sitkin Island 25 miles to the west and the volcano remains in a restless condition and is still considered hazardous to approach. The volcanic ash cloud produced by the eruption last week has dissipated and is no longer detected anywhere over Alaska in satellite data. A volcanic gas and aerosol cloud from the eruption is still present over parts of North America and the North Atlantic region, but has been dispersed by the wind and no longer is a single intact cloud.

AVO has received no new information about ash emissions or activity from passing pilots or mariners this week. Strong sulfur smell was reported by residents of Atka village yesterday and is likely coming from Kasatochi. The volcano is still quite restless and renewed eruptive activity remains a possibility. Should activity at the volcano resume, it is possible for ash clouds, ash fallout, and pyroclastic flows to develop and these could be as large or larger than those associated with the eruption on August 7.

Eruptive activity at Cleveland Volcano has occurred throughout the week, although the volcano has been obscured by clouds for a good portion of the week making observations by satellite difficult or impossible. Thermal anomalies at the summit were observed earlier in the week and a small ash plume was observed on the morning of August 12, but nothing has been observed since then. AVO has received no additional information or observations about activity at Cleveland.

Eruptive activity continues at Okmok Volcano although the general intensity of the eruption has declined throughout the week. The seismic intensity and tremor duration are still above background levels suggesting that minor ash and steam emissions are still occurring.

The levels of seismicity observed throughout the week indicate that Okmok may be moving toward a less explosive phase within its current eruptive cycle. Though it remains possible for strong explosive eruptive activity to resume with little or no warning, the general trend of activity this week has been one of gradual decline.

OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 30 volcanoes in Alaska. Satellite images of all Alaskan volcanoes are analyzed daily for evidence of ash plumes and elevated surface temperatures. Some volcanoes may currently display anomalous behavior but are not considered to be at a dangerous level of unrest. Augustine, Iliamna, Redoubt, Wrangell, Gareloi, Great Sitkin, Makushin, Fisher, Shishaldin, Isanotski, Pavlof, Veniaminof, Ugashik-Peulik, Griggs, Snowy, Fourpeaked, Aniakchak, Tanaga, Kanaga, Akutan, Westdahl, Dutton, Ukinrek Maars, Martin, Mageik, Trident, Katmai, Novarupta, Spurr, and Korovin volcanoes are in color code GREEN and volcano alert level Normal. All are at or near normal levels of background seismicity. AVO did not detect ash plumes or significant elevated surface temperatures in the vicinity of any volcano.

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

VOLCANO ALERT LEVELS

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORYVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.

WARNINGHazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES

GREENVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

YELLOWVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

ORANGEVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].

REDEruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].